Other Gas-Phase. Reactants

While one might expect that other tropospheric free radicals such as 0(3P), H02, and R02 could react with S02 as well, such reactions are not significant. 

Because the oxidants for S02 are generated in the VOC-NO. system discussed in Chapter 6, the overall gas-phase mechanism for the oxidation of S02 to h2so4 is quite complex. The reader is referred to the mechanism in the RADM model (Regional zlcid Deposition Model) for a treatment of the VOC-NO -S02 chemistry (Stockwell et al., 1990 Gao et al., 1996). It should be noted that an earlier version of this mechanism is given in some of the examples included with the OZIPR model discussed in Chapter 16 and whose applications are included with this book. 

For example, let us assume that the concentration of OH is constant. Then the rate of oxidation of S02 by OH, 

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